The present invention generally relates to vehicle brake systems and more particularly relates to a pressure fluid accumulator for use in vehicle brake systems.
A pressure fluid accumulator of this general type is disclosed in international patent application WO 98/37329. The media-separating element in the prior art pressure fluid accumulator is configured as a metallic pleated bellows, and the closure member of the bottom valve is connected to the end surface close to the hydraulic port of this bellows by means of a spring. To achieve effective closure of the hydraulic port, the closure member includes a rubber-elastic sealing element.
A shortcoming from which the prior art accumulator suffers is the condition that the closing slot which develops when the closure member moves to sit on the bottom is penetrated by the pressure fluid so that there is the imminent risk of damage or destruction of the sealing element and, hence, failure of the pressure fluid accumulator. Another disadvantage is seen in the escape of pressure fluid which may be caused by an expansion of the pleated bellows due to temperature variations.
In view of the above, an object of the present invention is to improve upon a pressure fluid accumulator of the above-mentioned type to such effect that damage of the bottom valve and inadvertent pressure fluid escape is prevented and, thus, the reliability in operation is considerably increased.
According to the present invention, this object is achieved in that the closure member can be moved by the media-separating element to adopt a position in which it fulfils the function of a hydraulic piston. This is achieved in that the closure member, upon approach of the end surface of the pleated bellows on the bottom, is moved into the hydraulic flow without inhibiting it, and subsequently, when floating in the hydraulic flow, is moved into abutment on a stop, with the result that the hydraulic port is closed in the way of a locked hydraulic piston.
To render the idea of the present invention more precise, the closure member is guided in a bore provided in the hydraulic port and includes at least one sealing element which provides a sealant vis-à-vis the wall of the bore. The bore is preferably configured as a stepped bore, and the sealing element cooperates with the small-diameter portion of the bore.